Essentially a condensed version of the episodes of the show.
Sometimes, these shrunk versions can be terrible, to the point of loosing all that the show can offer. But sometimes (mostly in the case of a short series) they cans still tell a story well enough to be entertaining.
Both are Mecha titles, and both are movie versions of the short series, and both are OAV quality (80/90's) animation. If you are looking to see the subsequent shows that these represent, yet do not have the time to hunker down for a long show, this might be the way to go.
Simon lives a boring life in the underground village of Jeeha, where his main job day in and day out is to dig tunnels. His close friend Kamina, however, longs to bust out of their oppressive existence and reach the surface world where open skies and adventure await! One day, during his usual digs, Simon discovers a robot with a big face buried amongst the rocks. No sooner has he shown Kamina his mysterious find when two beings from the surface crash land into Jeeha Village - one is a gun-toting woman calling herself Yoko and the other is a terrifying mecha piloted by a Beastman! Seeing their chance to escape village drudgery, Kamina rallies Simon and Yoko to defeat the invader using their new robot, Lagann. However, upon breaking out onto the surface world, Simon, Kamina, and Yoko encounter enemies more powerful than they could have envisioned. Their fight for adventure just turned into a war for the survival of the human race - will their lust for freedom hold out against such terrible odds?
The movie version!
These feature film compressions of the first half of Gurren Lagann and Gunbuster cover very similar series - enthusiastic, punchy Gainax takes on the mecha genre. And they're basically those titles re-edited to make a feature film, with a minimum of additional sheen added (a new ending in Guren-Hen, admittedly) and one of the principals mostly sidelined in the editing process (Rossiu and Jung Freud don't get much to do here.)
But hey. You want a Movie Verson of a very similar franchise with pretty similar results? Here you go.